Hippocrates and Aristotle proposed the idea of what they called pangenes, which they thought were tiny pieces of body parts. They thought that pangenes came together to make up the homunculus, a tiny pre-formed human that people thought grew into a baby. In the 1600s, the development of the microscope brought the discovery of eggs and sperm. Antonie van Leeuwenhoek, using a primitive microscope, thought he saw the homunculus curled up in a sperm cell. His followers believed that the homunculus was in the sperm, the father “planted his seed,” and the mother just incubated and nourished the homunculus so it grew into a baby. On the other hand, Regnier de Graaf and his followers thought that they saw the homunculus in the egg, and the presence of semen just somehow stimulated its growth. In the 1800s, a very novel, “radical” idea arose: both parents contribute to the new baby, but people (even Darwin, as he proposed his theory) still believed that these contributions were in the form of pangenes.
Homunculi are nearly indestructible and do not age. In addition, each one has a special, deadly power. For example, Lust can extend her nails to use as a deadly weapon and Sloth can transform from a solid state to that of a liquid. Homunculi become paralyzed when in close proximity to parts of their former bodies. The resulting paralysis or loss of consciousness often aids in one of the few ways to kill a homunculus: sealing via an alchemical array. This causes the homunculus to expel the red stones which fuel them, and results in the body of the homunculus dissolving and/or weakening. Most homunculi are incapable of using alchemy, but there are exceptions.